Epitaxial growth of GaInAsSb for thermophotovoltaic devices

The growth and characterisation of GaInAsSb alloys, lattice-matched to GaSb substrates. are reported with a particular focus on these alloys for therm ophotovoltaic (TPV) devices. Using a unique combination of organometallic p recursors, high-quality metastable GaInAsSb epitaxial layers with energy ga ps as low as 0.5 eV have been grown by organometallic vapour-phase epitaxy. The GaInAsSb material quality is significantly improved for growth at a lo wer growth temperature of 525 degrees C compared with 575 degrees C, and at a higher growth rate of 5 mu m/h compared with 1.2 mu m/h. 4 K photolumine scence full width at half maximum values are as low as 4.3 meV for 0.59 eV GaInAsSb and 9.5 meV for 0.5 eV GaInAsSb. The importance of the surface-ste p structure and growth kinetics on these metastable alloys is discussed. Un coated TPV devices incorporating metastable GaInAsSb, with energy gaps in t he range 0.495-0.549 eV, and a GaSb window layer exhibit an external quantu m efficiency (QE) of nearly 60%, which corresponds to an internal QE of 90% . The open-circuit voltage is 313 mV for the 0.549 eV device, and decreases to 239 mV for the 0.495 eV device.